The present invention relates to information recording methods and apparatuses which use a medium for recording information by irradiating an energy beam and more particularly, to an information recording method and medium which can exhibit excellent effects on a phase transition optical disk as well as to an information recording apparatus based on the information recording method.
In a related art method for performing recording and erasing operations over a rewritable recording film, for example, when an optical disk is used which has an exchange coupling two-layer film as a recording film as disclosed in U.S. Pat. No. 5,475,657, or when a phase transition type optical disk recording film is used which can erase information at high speed by realizing crystallization in substantially the same time as a laser irradiation time for recording as disclosed in JP-A-62259229 (laid-open on Nov. 11, 1987); the recording and erasing are carried out by changing energy of one energy beam to one of at least two levels higher than a reading power level, that is, by changing the energy of the energy beam to one of at least a high power level and an intermediate power level. This method is advantageous in that so-called overwriting (rewriting based on overwriting) of recording new information while erasing existing information can be realized. Further, as disclosed in JP-A-62259229 and JP-A-3-185629 (laid-open on Aug. 13, 1991), such a phenomenon that a recording mark becomes a tear drop shape can be suppressed (a backward width of the recording mark becomes larger than a forward width thereof) by changing the energy of an energy beam into one of three power levels, that is, high and intermediate levels and a level lower than the intermediate level.
In recent years, there has been put in practical use a DVD-RAM (digital video disk-random access memory) which uses a 120 mm-diametered disk made of phase transition material and having a memory capacity of 2.6 GB on its one side. A recording control method employed in this example is as shown in FIG. 1 and is explained as DVD Specification for Rewritable Disc (DVD-RAM), Part 1, Physical Specifications, version 1.0 (July, 1997), Page PHX-9, FIG. F-1.
JP-A-63-48617 (laid-open on Mar. 1, 1988) also discloses a method for changing an energy beam depending on a mark length (corresponding to a region length in a second state in claims at the time of its application) or on a space length (corresponding to a region length in a first state in claims at the time of its application).
Also disclosed in JP-A-8-287465 (laid-open on Nov. 1, 1996) is a method for converting an energy beam to a multi-pulsed train depending on a mark length or a space length.